Controled switching of octaves in an electronic musical instrument

ABSTRACT

A pedal tone section of an electronic musical instrument comprises tone generators of an octave, pedal keys of an octave having associated key switches, a latching selector operated by the key switches and sustainingly selecting one signal out of signals of the tone generators, an octave shifter including a through line and a binary divider selectively operated by a player, the octave shifter providing an output which is either a divided or nondivided signal of the latching selector output. A frequency divider further divides the octave shifter output and a pedal tone signal is generated. Preferably, manipulation of a knee lever operates the octave shifter to shift the tone pitch by an octave and as a result the compass of the pedal keyboard is extensible upward or downward without increasing the number of the pedal keys.

United States Patent [72] Inventor Makl Yamashita 3,150,228 9/1964 Gibbs et a] 84/DlG. 23 lllmlmllsll-filii Japan 3,155,762 11/1964 Thomas et al. 84/1 .01 12 1 pp No. 865,830 3,317,649 5/1967 Hearne 84/1.17 X Filed 6 3,488,515 111970 Hiyoshi 84/1.01 X 1 51 Patented a- 1 1 3,499,091 3 1970 Bunger..... 84/1.03 [73] Assignee Nippon Glkki Seizo Kabushiki Kaisha 3,006,228 10/1961 White 84/l.0l v Japan 3,150,228 9/1964 Gibbs et al 84/1.26 Priority 68 3,358,068 12/1967 Campbell 84/1.0I

/68 Primary Examiner-D. F. Duggan Assistant Examiner-Stanley J. Witkowski Auorney- Flynn & Frishauf [54] CONTROLED SWITCHING OF OCTAVES IN AN ELECTRONIC MUSICAL INSTRUMENT ABSTRACT: A pedal tone section of an electronic musical 1n- 7 Claims4bnwing Figs. strument comprises tone generators of an octave, pedal keys of an octave having associated key switches, a latching selec- US. tor p t d th k y it he and su tainingly electing one 84/DIG 25 signal out of signals of the tone generators, an octave shifter [5|] [litt. i l di a th h li nd a binary divide electively Gloh operated by a player, the octave shifter providing an output (50] Field of Search .1 84/1 .01, which is either a divided or nondivided Signal f the hitching L08 selector output. A frequency divider further divides the octave [5 6] Re Cited shifter output and a pedal tone signal is generated. Preferably, manlpulatlon of a knee lever operates the octave sh1fter to UNITED STATES PATENTS shift the tone pitch by an octave and as a result the compass of 2,922,329 l/ 1960 Hanert 84/DIG. 25 the pedal keyboard is extensible upward or downward without 3,039,346 6/1962 Martin 84/1.08 increasing the number of the pedal keys.

i TONE GENERATORS 15 17 18b 18 LATCHING 9! V 16b SELECTOR I I F\ r a... I z .-l2 PEDAL KEY 12 22 -2l 6 2O SWITCHES i F.F. F. F. Z LFF. I

' 23a 5 4 a 23b 23d 1 TONE KEYERS 8 TONE TONE FILTERS *{CONTROLS 2E? 33}- 24 16' TONE TONE FILTERS CONTROLS I5 BACKGROUND OF THE INVENTION This invention relates to a pedal compass extension system for an electronic musical instrument, and more particularly to a novel pedal compass extension system capable of practically extending the compass of the pedal keyboard by selectively shifting a pedal tone pitch.

ln usual keyboard type electronic musical instruments such as the electronic organ, there is provided a pedal operated keyboard section, in addition to an upper manual keyboard section mainly to play melodies and a lower manual keyboard section mainly to play accompaniments. The pedal keyboard section servers to give forth beats in the bass tone region. In popular model instruments, the pedal keyboard section usually consists of 13 pedal keys corresponding to 13 notes within one octave from C through C according to the musical notation (actual tones re between C and C as the pedal keyboard section is usually based on the 16' register).

As the entire compass of the pedal keyboard section of these electronic musical instruments is restricted within the range of one octave, it is impossible to play a composition whose compass for the pedal keyboard section exceeds one octave. Thus, a performance so rich in the power of expression of the performer as to give full satisfaction to himself can not be attained with an instrument having few pedal keys in the pedal keyboard.

It has been thought of to increase the number of pedal keys installed in order to extend the compass for the pedal keyboard section. However, to attain satisfactory performance, the number of the pedal keys should be increased to a considerable extent, and the increase of the pedal keys should be accompanied by extreme complication of the tone generators and associated circuits, thus leading to increased complexity and costs. Also, with an instrument provided with a pedal keyboard having an increased number of pedal keys, its operation would be extremely difficult, as there are extra keys to be operated and the key arrangement occupies a greater space. Extremely high technique will be required to smoothly operate such a pedal keyboard. Thus, to increase the number of pedal keys in the pedal keyboard section is practically undesirable, particularly for popular type electronic musical instruments.

The object of the present invention is to provide affairs into consideration, and its object is to provide a novel pedal section for electronic musical instruments which enables the compass of the pedal keyboard to be greatly extended without increasing the number of the pedal keys.

SUMMARY OF THE INVENTION According to the invention, the foregoing object is attained by a construction comprising tone generators, switches operated by respectively associated pedal keys, a latching selector sustainingly selecting one corresponding signal out of output signals from the tone generators in response to the operation of a corresponding key switch, an octave shifter including a shifting switch for the manipulation of a player, and at least a binary divider selectively rendered operative by the manipulation of the shifting switch and providing either a divided or nondivided signal of an output signal from the latching selector, a frequency divider further dividing an output signal from the octave shifter, and a keyer gating an output signal from the frequency divider in response to the operation of the key switches.

With this novel pedal compass extending system, outstanding broadening of the pedal keyboard compass is practically possible without requiring the operator to have any extra perfo.mance technique, as the pedal keyboard compass may be shifted by the selective connection or switching operation of he binary divider in the octave shifter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a circuit showing a preferred embodiment of the pedal compass extension system according to the invention;

FIGS. 2A and 2B are detailed diagrams of an actual circuit showing an example of the embodiment of FIG. 11; and

FIG. 3 is a block diagram of a circuit showing a main art of another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic construction of a first embodiment, and FIGS. 2A and 2B show a detailed construction of a preferred example thereof with component values indicated to facilitate practice of the invention by those skilled in the art of this field. Referring to FIG. I and FIGS. 2A and 2B, reference numeral I1 designates a group of oscillating-type tone generators providing each of 13 tones of from C (523 Hz.) through C (1,047 Hz.) out of more-in-number generators in the electronic musical instrument. The generators are flip-flops (bistable multivibrators) of a simplified construction in FIG. 2A, but any conventional type oscillators may be used instead. A numeral l2 designates a group of pedal key switches including 13 pairs 12a and 12b 12a and l2b of switches, each pair consisting of a first key switch 12a, (...l2a, and a second key switch 12b 12) corresponding to each of 13 pedal keys of from C note through C note. A numeral 13 designates a latching selector which receives tone signals from the one generators 11, and leads out only one of them at a time according to the operation of the first key switch 12m (...l2a|:r) by the depression of a pedal key (not shown) and sustains the connection ofthe lastly selected signal until another pedal key is next depressed. A mostpreferable construction of the latching selector is shown in FIG. 2A by the numeral 13, which consists of 13 R-S flip-flops 13a, 13a each acting as a shunt switch for a respective tone signal with all signals shunted except one at a time and is controlled by the operation of the first key switches 12a, The construction and operation of such a latching selector is described in detail in US. Pat. No. 3,488,515 to Teruo Hiyoshi and as signed to same assignee as the present invention. When any one of the pedal keys in the pedal keyboard is pushed down by foot only one of the first key switches 12a, to 12a corresponding to the operated pedal key is closed to turn off the corresponding one of the flip-flop circuits 13a to 13a through a voltage terminal V,. This ceases the shunting of the tone signal applied to the corresponding one of the flipflop circuits and permits the signal to be fed to an output terminal 13b, and at the same time keeps all the other flip-flop circuits in the on state to thereby shunt the rest of he tone signals so that they are not fed out to the output terminal 1311. Thus, only that single tone signal which has been led from the associated tone generator to the pertinent flip-flop circuit is sent forth from output terminal 13b Thus, only that signal which has been led from the associated tone generator to the pertinent flip-flop circuit is sent forth from output terminal 13b of the latching selector circuit 13. The tone signal at a required pitch (frequency) thus selectively led out of output terminal 13b of the latching selector circuit 13 is impressed through an amplifier 5 upon an octave shifter 16 of he construction to be described hereinafter, the amplifier 15 being a kind of pulse modifier having circuit construction as shown in FIG. 2A.

The octave shifter 16 includes a binary or one-half frequency divider 17, for instance, consisting of a flip-flop circuit and a double-throw switch 18. The binary divider 17 has its input terminal in connection to the output terminal of the amplifier l5 and its output terminal connectable through a first fixed contact 18a and movable contact piece of switch 18 to the input terminal of a frequency divider circuit 19 to be described hereinafter in more detail. A second fixed contact 1812 of the switch 18 is 'directly connected to the input terminal of he binary divider 17. Thus, when the movable contact piece 180 is thrown to the first fixed contact 18a, the binary divider 17 is electrically inserted between the amplifier and the frequency divider circuit 19, whereas upon switching-over of the movable contact to the second fixed contact 18b, the input and output terminals of the binary divider 17 are short-circuited, thus electrically removing the binary divider 17 from between the amplifier 15 and the frequency divider circuit 19. Accordingly, depending upon the state of connection of he switch 18, the tone signal at a certain pitch in a range between C (523 Hz.) and C (1,047 Hz.) selectively derived out from the output terminal 13b of the latching selector circuit 13 is fed to the frequency divider circuit 19 either through the binary divider 17 as a tone signal shifted in pitch by one octave to the lower range of between C, (262 Hz.) and C (523 1-12.), or directly as a tone signal in the range between C and C The tone signal fed to the frequency divider circuit 19 through the octave shifter circuit 16 is subjected to frequency division to shift down its tone pitch to the range between C, (33 Hz.) and C, (65 Hz.) so that it becomes suitable as pedal tone. Frequency divider circuit 19 consists, for instance, of three cascade-connected flip-flop circuits or one-half frequency dividers 20, 21 and 22 whereby the tone signal supplied to the input terminal of frequency, divider circuit 19 is subjected to successive frequency divisions, thereby producing signals of tones successively lower in tone pitch by one octave. Thus, at the output terminals of one-half frequency dividers 20, 21 and 22 there becomes available first, a second and a third frequency-divided signals of ones successively lower in one pitch by l, 2 and 3 octaves than the tone of the input signal supplied to frequency divider circuit 19.

The third and the second one signals obtained at output terminals of the one-half frequency dividers 22 and 21 and the second and the first tone signals obtained at output terminals of the one-half frequency dividers 21 and are respectively synthesized (mixed) through respective combinations of resistors 23a and 23b, and resistors 23c and 23d to produce two tone signals (for a 16 register and an 8 register) which are respectively supplied to input terminals 14a, and 14a of the tone keyer circuit 14. ,The tone keyer 14 consists of two keyers 14c, and 140 each including a transistor amplifier. Each of the keyers 14c, and Me, is energized, through a source terminal V., only when one of the second key switches 12b, to 12b, of the pedal key switches 12 is closed, to permit passage of the tone signals fed to the input terminals 14a, and 14a, to the output terminals 14b, and 1%,. A capacitor 1 1d causes the tone signals to decay gradually after the key switch 12b, ("1212",) is opened. and as a result provides a sustain effect. r T e 19!? ,s sna sfstt elf d.3ltssi slcd tho the tone keyer circuit 14 to the output terminals 141), and 14b thereof as the result of operating the corresponding pedal key of the pedal keyboard are respectively fed to 16' tone filters and 8 tone filters 25. By these tone filters 24 and 25, there are generated respective tone signals corresponding to the desired voices, i.e. tone signals whose waveforms are so shaped as to provide sounds of desired tone colors, on the basis of the input tone signals. The shaped tone signals from the 16' and the 8 registers are synthesized (mixed) in suitable proportions through tone controls 26 and 27, and the synthesized tone signal is amplified by an amplifier 28 prior to being fed to the following stage including for example, an expression control, a power amplifier and a speaker, as in the conventional electronic organ to produce musical tone at the required tone pitch in the gamut for the pedal keyboard section.

The movable contact piece 18c of the switch 18 the octave shifter 16 is ordinarily in connection to the first fixed contact 18a. The switch 18 may advantageously be of an automatically returning type, for instance, incorporating a knee lever capable of being operated by a right knee of the player at any time during music performance, and may be so arranged that only when it is operated by depressing the knee lever rightward, the state of connection of the contact piece 180 to the first contact 18a is switched over to the side of the second contact 1812.

The operation of the pedal compass extension system of the foregoing construction in accordance with this invention is now described, When the movable contact piece 180 of the switch 18 in the octave shifter 16 is in connection to the first fixed contact 18a, upon pedalling a required one of the aligned l3 pedal keys of the pedal keyboard, for instance, the

fourth pedal key from the right having to the note name A in the musical notation, a tone signal having a pitch of A (880 Hz.), hereinafter termed as a tone signal A is selectively led out from the output terminal 13b of the latching selector 13. The tone signal A, is then amplified by the amplifier 15 and fed to the octave shifter 16, where it undergoes frequency division. As the state of connection of the switch 18 is such that the one-half frequency divider 17 is electrically inserted, the tone signal A, transformed into a tone signal A, (440 Hz.) one octave lower prior to being fed to he frequency divider circuit 19, where it undergoes successive frequency divisions by the flip-flop circuits 20, 21 and 22 respectively serving as one-half frequency dividers to produce tone signals A;, (220 112.), A Hz.) and A, (55 Hz.) at the output terminals of the flip-flop circuits respectively. As is described, the tone signals A, and A and tone signals A, and A are respectively synthesized (mixed) to produce composite tone signal having pitch of A, for the 16' register and a composite tone signal having a pitch of A for the 8' register. As the aforementioned pedal key of the pedal keyboard is being pushed down, the tone signals for the 16 and 8 registers are fed through the tone keyers 14 to respective tone filters 24 and 25 wherein these signals are shaped to have a desired tone color. The shaped tone signals of A, for the 16' register and of A for the 8' register are mixed at suitable proportions through the tone controls 26 and 27, and the mixed tone signal is amplified by the amplifier 28 and fed to the following stage of the instrument. Thus, the tones corresponding to the pedal by name A the tone A, being the 16' tone and the tone A, being the 8 tone therefor, are played (emitted from a speaker) by operating the pedal key having a key name A in the musical notation.

When the movable contact piece of the switch 18 in the octave shifter 16 is switched over to the second fixed contact 18b, which is attained, for instance, only when the aforementioned knee lever is under operation, tone signal A, led out from the output terminal 13b of the latching selector 13 is fed to the frequency divider circuit 19 directly, i.e., without passing through the one-half frequency divider 17. Accordingly, at the output terminals of the frequency dividers 20, 21 and 22 are obtained tone signals A, (440 112.), A (220 Hz.) and A (110 HZ.) which are one octave higher in pitch than the respective counterparts in the preceding case, so that the tones corresponding now tones the pedal key name A,, the tone A, being the 16 tone and the tone A, being the 8 tone therefor, are played by operating the pedal key having the key name A This means that the pedal key A, now serves as a pedal key A in the region outside the provided keyboard.

As has been described, with the pedal compass extension system of the foregoing construction according to the present invention, musical tones which are different from each other in pitch by one octave may be selectively obtained by operating the same pedal key and merely switching the switch 18. Though the above description is concerned about the case of operating the pedal key having a key name of A in the musical notation, similar results may of course be obtained by operating any other pedal key of the pedal keyboard. Thus, with the pedal compass extension system according to the present invention, it is possible to play music both in one octave compass between C and C in the musical notation as is available with the usual electronic musical instruments and in the other selective one octave compass between C, and C.,, which is one octave higher, by operating the same pedal keyboard having only 13 keys from C through C by merely switching over the states of connection of the switch 18 of the octave shifter 16. Accordingly, by arranging such that the connection of the switch 18 may be switched over at any time during music performance by means of, for instance, a knee lever, with an electronic musical instrument having this pedal compass extension system, it is possible to extend, with only 13 pedal keys for one octave compass in the pedal keyboard the gamut of the pedal keyboard to a range of two octaves between C and C in the musical notation, which would require 25 pedal keys with the conventionally designed musical instrument of this type. Also, since fewer pedals are required in the present invention play compositions whose scores for the pedal keyboard cover a two-octave range between C and C in the musical notation are more freely executed andwith simple playing technique.

FIG. 3 shows a modified embodiment of the pedal compass extension system according to the present invention. it shows only a modified part, the octave shifter 16, in the embodiment shown in FIGS. 1, 2A and 2B.

ln this embodiment, the gamut for pedal keyboard may be extended not only to the higher region but also to the lower region equally by one octave. As is illustrated, the modified octave shifter 16 includes the scale-ofifour divider 29 for onefourth frequency division, for instance, consisting of two flipflop circuits connected in cascade and the second switch 30 in addition to the binary divider l7 and the first switch 18. Similar to the previous embodiment, the binary divider 17 is arranged to be inserted between the output terminal of amplifier and the input terminal of the frequency divider circuit 19 through the movable contact piece 180 and the first fixed contact 18a of the switch 18. The second fixed contact 18b of the first switch 18 is normally connected through a movable contact piece 30c and a first fixed contact 30a of the second switch 30 to the input terminal of the binary divider l7, and the scale-of-four divider 29 is connected between the input terminal of the binary divider 17 and a second fixed contact 30b of the second switch 30.

The construction of the first and second switches particularly convenient for performance may be attained, for instance, by forming the first switch 18 with an automatic-return type knee lever normally connected to the side of the first fixed contact 18a as in the previous embodiment and forming the second switch 30 with an operating switch provided on an operation panel as in various stops capable of switching-over at any rest time during performance.

The operation of the pedal key compass extension system of the above described construction according to the present invention is now described. When the movable contact piece 300 of the second switch 30 is in connection to the first fixed contact 30a, the circuitry is the effective equivalent to the pedal compass extension system of the previous embodiment, so that entirely the same results as in the previous embodiment may be obtained. When the state of connection of the second switch 30 is switched over to the side of the second fixed contact 30b, a tone signal having a certain tone pitch, for instance A selectively led out from the output terminal 13b of the latching selector l3 undergoes the action of the binary divider 17, if the movable contact piece 18c of the first switch 18 is thrown to the side of the first fixed contact 180, to produce the resultant tone signal A,,, whereas it is subject to the action of the one-fourth frequency divider 29 upon operating the first switch 18 to switch the movable contact piece 180 over to the second fixed contact 18b to produce the resultant tone signal A;,, with the resultant tone signal either A or A being subsequently fed to the frequency divider circuit 19. As will be readily apparent, it is possible to play music both in the oneoctave compass between C and C in the musical notation as in the usual electronic musical instruments and in a one-octave compass between C and C (one octave lower) in the musical notation with the same pedal keyboard having only [3 keys from C through C by merely altering the state of connection of the switch 18.

Accordingly, by arranging such that the first and second switches may be operated at any time during musical performance in the similar manner to the preceding embodiment, it is possible with an electronic musical instrument having this pedal compass extension system and only 13 pedal keys for one-octave compass to extend the gamut for the pedal keyboard section to cover 3 octaves between C and C it would require 37 pedal keys for a three-octave compass to be provided for the pedal keyboard section of a conventionally designed electronic musical instrument.

As has been described in the foregoing, with the pedal compass extension system according to the present invention, it is possible to selectively shift the compass of tones of tone signals fed to the tone filters in response to the operation of the pedal keys in the pedal keyboard by one octave (or more if so constructed) in both higher and lower directions with respect to the principal range of the pedal keyboard by merely operating the switch of the octave shifter, thereby extending the range of the pedal keyboard selectively in either the higher or lower direction. Thus, with an electronic musical instrument having the pedal compass extension system according to the invention, though the pedal keyboard consists of, for'instance, only 13 keys for one-octave compass, music performance with the range of the pedal keyboard section covering a few octaves may be accomplished by the mere addition of an extremely simple playing technique of operating the switches during the performance. This aids in greatly increasing the capacity of promoting the power of expression by virtue of the pedal keyboard section without requiring any particular high technique of performance and without increasing the number of the pedal keys, but with the addition of the aforementioned extremely simple means. In conclusion, the pedal compass extension system according to the present invention will provide outstanding effects when it is applied to the usual popular type electronic musical instrument which has few pedal keys and is mostly played by performers who have not acquired a relatively high playing technique.

What I claim is:

l. A pedal compass extension circuit device comprising:

pedal keys;

a plurality of tone generators;

key switches operated by respectively associated pedal keys;

a latching selector coupled to said switches for sustainingly selecting one corresponding signal from said tone generators in response to the operation of a corresponding key switch by a pedal key;

an octave shifter coupled to the output of said latching selector and including at least a binary divider and a shifting switch means adapted to be manipulated by a player, said binary divider being selectively rendered operative by the manipulation of said shifting switch means, said octave shifter dividing the output of said latching selector when said binary divider is rendered operative and said octave shifter passing the output of said latching selector undivided when said binary divider is inoperative;

a frequency divider further dividing the output signal from said octave shifter; and

means keying an output signal from said frequency divider in response to the operation of said key switches by said pedal keys.

2. The pedal key compass extension circuit according to claim 1, wherein said shifting switch means of said octave shifter includes a switch means having:

first and second fixed contacts, said first fixed contact being connected through said binary divider to the output terminal of said latching selector, said second fixed contact being connected directly to said output terminal of said latching selector; and

a movable contact piece adapted to be manipulated by said player connected to the input terminal of said frequency divider circuit.

3. The pedal compass extension circuit according to claim 1, wherein said octave shifter further includes a scale-of-four divider and wherein said shifting switch means includes first and second switch means respectively having first and second fixed contacts, and movable contact pieces, the first fixed contact of said first switch means being connected through said binary divider to the output terminal of said latching selector, the second fixed contact of said first switch means being connected directly to a movable contact piece of said second switch means, said first contact of said second switch means being connected directly to the output terminal of said latching selector, the second contact of said second switch means being connected through said scale-of-four divider to the output terminal of said latching selector, and a movable contact piece of said first switch means being connected to the input terminal of said frequency divider circuit.

4. The pedal compass extension circuit according to claim 2, wherein said switch means is an automatic return type knee lever switch means, said movable contact piece being normally in connection with said first fixed contact and being connected to said second fixed contact only during the operation of said switch means.

5. The pedal key compass extension circuit according to claim 3, wherein said first switch means is an automatic return type knee lever switch means, said movable contact of said first switch means being normally in connection with the first fixed contact of said first switch means and being connected to the second fixed contact of said first switch means only during the operation of said first switch means.

6. The pedal compass extension circuit device according to claim 1 comprising 13 pedal keys.

7. The pedal compass extension circuit device according to claim 6 wherein each of said pedal keys corresponds to respective tones within at least two different octaves of the musical scale. 

1. A pedal compass extension circuit device comprising: pedal keys; a plurality of tone generators; key switches operated by respectively associated pedal keys; a latching selector coupled to said switches for sustainingly selecting one corresponding signal from said tone generators in response to the operation of a corresponding key switch by a pedal key; an octave shifter coupled to the output of said latching selector and including at least a binary divider and a shifting switch means adapted to be manipulated by a player, said binary divider being selectively rendered operative by the manipulation of said shifting switch means, said octave shifter dividing the output of said latching selector when said binary divider is rendered operative and said octave shifter passing the output of said latching selector undivided when said binary divider is inoperative; a frequency divider further dividing the output signal from said octave shifter; and means keying an output signal from said frequency divider in response to the operation of said key switches by said pedal keys.
 2. The pedal key compass extension circuit according to claim 1, wherein said shifting switch means of said octave shifter includes a switch means having: first and second fixed contacts, said first fixed contact being connected through said binary divider to the output terminal of said latching selector, said second fixed contact being connected directly to said output terminal of said latching selector; and a movable contact piece adapted to be manipulated by said player connected to the input terminal of said frequency divider circuit.
 3. The pedal compass extension circuit according to claim 1, wherein said octave shifter further includes a scale-of-foUr divider and wherein said shifting switch means includes first and second switch means respectively having first and second fixed contacts, and movable contact pieces, the first fixed contact of said first switch means being connected through said binary divider to the output terminal of said latching selector, the second fixed contact of said first switch means being connected directly to a movable contact piece of said second switch means, said first contact of said second switch means being connected directly to the output terminal of said latching selector, the second contact of said second switch means being connected through said scale-of-four divider to the output terminal of said latching selector, and a movable contact piece of said first switch means being connected to the input terminal of said frequency divider circuit.
 4. The pedal compass extension circuit according to claim 2, wherein said switch means is an automatic return type knee lever switch means, said movable contact piece being normally in connection with said first fixed contact and being connected to said second fixed contact only during the operation of said switch means.
 5. The pedal key compass extension circuit according to claim 3, wherein said first switch means is an automatic return type knee lever switch means, said movable contact of said first switch means being normally in connection with the first fixed contact of said first switch means and being connected to the second fixed contact of said first switch means only during the operation of said first switch means.
 6. The pedal compass extension circuit device according to claim 1 comprising 13 pedal keys.
 7. The pedal compass extension circuit device according to claim 6 wherein each of said pedal keys corresponds to respective tones within at least two different octaves of the musical scale. 